IADR Abstract Archives
Stress Regulation of Rhamnose Biosynthesis in Streptococcus mutans
Objectives: The cariogenic bacterium Streptococcus mutans, a member of the oral flora, possesses a cell wall that is crosslinked with polysaccharides, termed the rhamnose-glucose polysaccharides (RGP). Previous studies have demonstrated an integral role for the RGP structures in virulence of S. mutans, cell division, and stress responses. A majority of the genes involved in the construction and transport of RGP to the cell surface are encoded in one operon. While the operon has been shown to be co-transcribed, very little is known about its regulation. RmlD, the enzyme catalyzing the final step in the production of the polysaccharide dTDP-L-rhamnose, is the first gene in the RGP operon.
Methods: We used transcriptional reporter fusions to measure expression of rmlD in conditions of environmental stress. Bioinformatic analysis of the RGP operon was performed using consensus sequences of known regulators in S. mutans.
Results: We demonstrated that exposure of S. mutans cultures to sublethal amounts of H2O2 and HCl resulted in a significant increase in rmlD expression. Sequence analysis revealed multiple putative binding motifs for 32 different transcription factors. The results demonstrate that rmlD expression is altered, compared to the parent strain, in backgrounds lacking known regulators involved in the response to acid and oxidative stresses.
Conclusions: As the only known function of RmlD is to produce dTDP-L-rhamnose and S. mutans is unable to break down rhamnose, the increase in rmlD activity may lead to an increase in RGP biosynthesis. These findings indicate that environmental stressors play a role in altering the cell wall physiology via mechanisms yet to be revealed.
Methods: We used transcriptional reporter fusions to measure expression of rmlD in conditions of environmental stress. Bioinformatic analysis of the RGP operon was performed using consensus sequences of known regulators in S. mutans.
Results: We demonstrated that exposure of S. mutans cultures to sublethal amounts of H2O2 and HCl resulted in a significant increase in rmlD expression. Sequence analysis revealed multiple putative binding motifs for 32 different transcription factors. The results demonstrate that rmlD expression is altered, compared to the parent strain, in backgrounds lacking known regulators involved in the response to acid and oxidative stresses.
Conclusions: As the only known function of RmlD is to produce dTDP-L-rhamnose and S. mutans is unable to break down rhamnose, the increase in rmlD activity may lead to an increase in RGP biosynthesis. These findings indicate that environmental stressors play a role in altering the cell wall physiology via mechanisms yet to be revealed.